1. Field of the Invention
The present invention concerns a multi-layer ceramic capacitor in which an internal electrode is constituted with a base metal and it particularly relates to a multi-layer ceramic capacitor using Cu for the internal electrode.
2. Description of the Related Art
For multi-layer ceramic capacitors used for electronic equipments such as portable equipments and telecommunication equipments, a demand for reducing the size and increasing the capacitance has been increased more and more. Further, a demand has been increased also for the reliability, and a multi-layer ceramic capacitor with a flat temperature characteristic (TC) for permittivity and having a good high temperature acceleration life time property characteristics (hereinafter referred to as “life time property”) has been demanded.
As means for obtaining the multi-layer ceramic capacitor of smaller size and large capacitance described above, JP-A No. 5-9066, for example, discloses a method of using a non-reduction dielectric substance porcelain composition. However, various additives are added in such a dielectric substance porcelain composition for providing anti-reducing property. Therefore, a baking temperature of 1,100° C. or higher was necessary for sintering the dielectric substance porcelain composition. Further, also for the internal electrode, a high melting Ni had to be used.
On the other hand, a multi-layer ceramic capacitor using a material capable of being baked at a low temperature of about 1,000° C. in view of the energy efficiency has been proposed. For example, JP-A No. 5-217426 discloses a non-reducing dielectric substance porcelain composition capable of being baked simultaneously with an inner electrode material such as Cu. However, since the dielectric substance porcelain composition described above has a low permittivity although the temperature characteristic is flat and it is difficult to obtain a small size and large capacitance multi-layer ceramic capacitor.
Further, for obtaining a multi-layer ceramic capacitor having a flat temperature characteristics and high permittivity (ε≧2,000), JP-A No. 10-308321, for example, discloses a method of using a dielectric substance porcelain comprising sintered grains having a core-shell structure. It is necessary in the core-shell structure to diffuse additives such as Mg in the crystal grains. However, diffusion of the additives in the crystal grains requires a baking temperature of 1,100° C. or higher.